1. Field of the Invention
Embodiments of the present invention generally relate to methods and apparatus for treatment of stormwater runoff, and more particularly to a stormwater treatment system employing dual vortex separators for removing debris and suspended particles from such stormwater runoff.
2. Description of the Related Art
Drainage systems for receiving fluid flow are well known in the art. Such systems provide a path for fluid flow from surface areas and often transport the fluid from surface areas directly to the ocean, rivers, lakes, estuaries, streams and the like without regard to the removal of debris, pollutants or other contaminants. For example, because of the Federal Environmental Protection Agency's Clean Water Act, controlling pollution from stormwater runoff is receiving ever-increasing attention at all levels of government, Federal, State and local. Federal and state agencies have issued mandates and developed guidelines regarding the prevention of non-point source (stormwater caused) pollution that require local government action.
Because of the aforementioned mandates, many cities and special districts have developed plans and taken steps to prevent stormwater pollution. These actions range from those that are educational in nature (labeling stormwater inlets with phrases such as “No dumping—Flows into Rivers and Streams”) to active measures to remove pollutants. Such measures generally require the installation of equipment for removing contaminants somewhere between where the stormwater enters the drainage system and the ultimate body of water receiving the runoff.
Several types of equipment are employed to reduce pollution and contaminants from stormwater runoff. Catch basin filtration systems use devices installed at the point that the stormwater enters the drainage system. The water flow is directed through an installed adsorbent material that aids in removing contaminants from the stormwater while allowing the water to flow into the drainage system. Such a permanently installed catch basin filtration system is disclosed in U.S. Pat. No. 5,720,574. In addition to catch basin filtration systems, oil/water separators have been employed. Such systems generally comprise large underground holding tanks that allow pollutants to settle in the tank and the water to flow into the drainage system. Other systems also exist to remove contaminants from water runoff. However, these systems are also generally permanent installations that are expensive to install and maintain.
Moreover, because such filtration systems typically require regular maintenance, issues arise such as ease of access and the length of time that a system can operate between cleaning or replacing filter elements or other parts. Access to elements that must be cleaned or replaced is problematic in some systems, such that a heightened burden is placed on those who regularly maintain these systems. In addition, silt, sediment and other debris tend to settle on or around filter elements in many filtration systems, such that the length of time that these elements can effectively filter stormwater runoff can be significantly reduced.
Another significant problem that has emerged in the development of catch basin filtration systems is the ability of such systems to process large quantities of fluid during peak flow periods without having backups or stoppages that result in localized flooding of surrounding areas. Peak flow periods would include, for example, extreme storm conditions or other flood type events. Due to concerns over storm drainage backups that can result in localized flooding, many filtration systems must employ some form of a high-flow bypass feature that allows excess fluids to proceed through the drainage system without being filtered during such high flow periods. As a result, these types of filtration systems have an upper limit as to the amount of fluid that can be filtered at any given time as well as a maximum capacity for the amount of fluid that can be passed through the system in any event.
As an alternative to, or in combination with use of inlet catch basins, it has been suggested to direct flows of stormwater runoff to larger, downstream structures, i.e., catch basins or manholes, accessible by manhole cover, into which some sort of treatment apparatus has been placed. In association with use of these larger basins, it has been proposed to use a hydrodynamic separation unit, these types of separators well known for wastewater treatment, to remove suspended particles from runoff. However, the units currently available require custom installation, and like the inlet catch basin filtration systems earlier described, require periodic maintenance to remove accumulated sludge and debris. Because of the configuration and lack of portability of these units, they do not allow for easy cleaning of the manhole into which they have been placed.